Sum-of-the-Years'-Digits Convention

The sum-of-the-years'-digits depreciation method applies a midmonth convention, giving a full month's depreciation in the acquisition month if you purchase the asset on or before the 15th of the month. If you purchase the asset after the 15th, no depreciation is allowed. In the disposal month, if you dispose of the asset on or before the 15th, no depreciation is allowed; if you dispose of the asset after the 15th, a full month's depreciation is allowed.